Support in ships of tanks designed to carry low temperature liquids



Oct. 25, 1966 J. F. LEATHARD 3,280,773

SUPPORT IN SHIPS 0F TANKS DESIGNED TO CARRY LOW TEMPERATURE LIQUIDSFiled March 9, 1962 2 Sheets-Sheet l mmkzggz we QM M A ttornegs Oct. 25,1966 F. LEATHARD 3,280,778 SUPPORT IN SHIPS OF TANKS DESIGNED TO CARRYLOW TEMPERATURE LIQUIDS Filed March 9, 1962 2 Sheets-Sheet z h A L n.u", I I, I ,1

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tlorneyS United States Patent p This invention concerns the support oflarge size cargo tanks in ships which are to carry low temperatureliquids, and wherein the tanks are separated from the main structure ofthe ship.

The problem that exists is to anchor the tanks securely so that theywill not shift as the ship heaves and pitches, while at the same timeallowing the tanks to undergo the considerable thermal movements thatoccur when the cargo is, for example, a low temperature liquefied gaslike liquid methane.

If the case of an upright cylindrical tank be taken, vertical expansionand contraction of the tank may be considered to take place with respectto a horizontal plane represented by the bottom of the tank. Radialexpansion and contraction of the tank structure may be considered totake place with respect to a vertical line represented by the verticalaxis of symmetry of the tank.

According to the present invention, each tank is constrained fromlateral bodily movement with respect to the ships hull structure, whilebeing left free to expand and contract laterally, by means of at leasttwo substantially horizontal keys that connect the tank bottom to thehull structure by being secured to one and received in key-ways orchannels of the other, the two keys extending across the tank bottom atan angle to one another.

Although in what follows it is assumed that the tank is symmetrical andmounted vertically in the ship, the invention is not limited to tanks ofthis shape but the principles involved may be applied to tanks of almostall shapes. A necessary requirement, however, is that the bottomstructure of the tank should be designed so that the supports to bedescribed are located at strong places in the structure. In the case ofcylindrical tanks this implies that the stiffening in the bottom of thetank should be radial in form.

It is unlikely that loads other than vertical loads would require to beaccepted by the supports when thermal movements are taking place, Whenthe ship is at sea the tank is at virtually constant temperature andconsequently no thermal movements take place. It is then that thesupports must be capable of providing lateral restraint because of shipmovement, as well as vertical support to accept the Weight of the tank.Vertical loads may be taken on a series of heat-insulating stoolserected on the inner bottom of the ships structure. Various ways ofcarrying the invention into eifect will now be described by way ofexample, reference being had to the accompanying drawings in which:

FIGURE 1 is a diagram showing the arrangement of a vertical load bearingtank support for a ships liquefied gas cargo tank, and

FIGURE 2 is a diagram of the arrangement of a key and cooperating keywayor channel connecting the tank bottom to the ships hull structure.

In FIGURE 1, a large ships cargo tank of upright cylindrical form tocontain liquefied gas, such as liquid methane or natural gas, rests onstools 11 that stands on the ships inner bottom plating 12 and one ofwhich is shown. These stools 11 are designed to provide acceptableinsulation between the tank bottom structure and the ship structure fromthe point of view of heat leakage.

- Patented Oct. 25, 1966 Each stool 11 is arranged below a radial web 13of the tank bottom and contact between the tank bottom and the stool isthrough the medium of a ball-dolly 14 which will allow for radialmovements of the bottom of the tank relative to its central axis, whileat the same time providing vertical support and minimising the heatleakage path. The ball 15 of the ball-dolly 14 engages a bearing plate16 on the underside of the tank bottom plating 17.

The ball-dolly 14 is carried on a steel plate 18 overlying a block ofhard insulating material 19, such as that known under the registeredtrademark Permali, and this block is in turn supported by timber stoollegs 20. The legs 20 can be of pinewood for example, and they aresplayed and joined near their converging upper ends by wood gussets 21.A plate .ring 22 encircles the joint between the tops of the legs 20 andthe block 19 for reinforcing purposes, while the lower ends of the steellegs 20 are received in steel foot bearers 23.

Lateral restraint for the tank is provided by two key members,preferably, but not necessarily, set at to each other and extendingdiametrically across the bottom of the tank. The angle between the twokeys and the angle at which each key is set in relation to the fore andaft centre line of the ship, are to be determined from consideration ofthe relative lateral restraints required due to heaving, and due topitching, or a combination of such ship movements.

A particular arrangement of such a key is shown in FIGURE 2 in whichcontact between the tank bottom structure 10 and a stool 24 is providedthrough the me dium of inclined ball-dollies 25, 26, whilst the stool isdesigned as before to provide adequate insulation between the tank andthe inner hull structure of the ship. The two series of ball-dollies 25,26 are set at an angle to the vertical, for example 35 to 40, that isselected so that lateral expansion of the tank is permitted while at thesame time the desired lateral restraint is provided.

The key is constituted by a row of insulating blocks 27 of Permali orthe like each having upwardly-converging inclined side faces 28 anddownwardly-converging inclined under faces 29. Each block 27 issupported on widely splayed pairs of timber stool legs 30 joined to thefaces 2'9 and with their lower ends received by foot bearers 31 on theships inner bottom 12, Adjacent pairs of stool legs 30 are tied to oneanother by clamping bolts 40.

A bent steel plate 32 forms a reinforcing cladding for the top andinclined sides 28 of the block 27, and its lower edges are extendedbeyond the block so as to make, together with angle bars 33 at theinside of the upper ends of the legs, the joints between the block 27and the stool legs 30. The ball-dollies 25, 26 are borne on the inclinedfaces of the plate 32.

A series of brackets 41 welded to the underside of the tank bottomplating 17 are formed with recesses 34 and carry oppositely-inclinedplates 35 within these recesses at opposite sides thereof to form thekeyway or channel for the key. The balls 36 of the ball-dollies 25, 26en gage bearing plates 37 borne by the plates 35. As in the case of theweight-bearing stools 11, the rows of stools 24- are disposed underradial webs 13 of the tank bottom structure 10, which structure alsocomprises circumferenti-al webs 38 and top plating 39.

An alternative arrangement consists in providing two metallic or hardwood keys set at suitable angles on the underside of the tank bottomwhich engage in channels provided in solid balsawood, or some similarform of insulation, lining the inner bottom of the vessel. Or again, theoutside of the bottom of the tank may be lined with solid balsawood orother suitable insulation and similar keys may engage in channels in thebalsawood, these keys being attached to the inner bottom of the vessel,or

if access is required, set on stools on the inner bottom of the vessel.

I claim:

1. The combination in a ship of a cargo tank to contain bulk lowtemperature liquid and a tank mounting to constrain said tank fromlateral bodily movement with respect to the ship while leaving the tankfree to expand and contract thermally, comprising two series of stoolsanchored on the ships inner bottom in rows extending in two horizontaldirections at an angle to each other and diametrically of the bottom ofthe tank thereby to constitute two discontinuous keys, each stool havingside faces that are each inclined to the vertical at an angle of about35 to 40 whereby said discontinuous keys constituted by said stools eachhave sides that converge upwardly toward a key apex, two series oftunnel-form brackets secured to the underside of said tank in twohorizontal rows parallel to and in substantial alignment vertically withsaid keys and having downwardly-opening recesses with sides that divergedownwardly, said recesses being in alignment along the rows to definetwo keyways having downward divergence corresponding to the upwardconvergence of said keys, each row of said tunnel-form brackets beingdirectly over a respective one of said keys with an upper portion of thekey including the apex thereof entering the keyway defined 'by said row,antifriction ball means mounted on said inclined side faces of saidstools just below the apices thereof, and hard plates secured to saiddiverging sides of the recesses of said tunnel-form brackets whichplates bear on said antifriction ball means and transmit lateral andvertical forces between the tank and said stools.

2. A tank according to claim 1, wherein said keys extend beneath radialstilfeners of the tank bottom.

3. A tank according to claim 1, wherein each stool comprises a block ofa hard heat-insulating material with inclined faces and supported ontimber stool legs.

4. A tank according to claim 1, and wherein the tank weight is borne bystools upstanding from the ships inner bottom and disposed under radialstifieners of the tank bottom structure.

5. A tank according to claim 4, wherein each stool is of aheat-insulating character and bears at its top face anti-friction means,such as a ballbearing, interposed between the stool and the underside ofthe tank.

6. A tank according to claim 5, wherein each weightbearing stoolcomprises a block of a hard heat-insu1ating material supported on timberstool legs.

References Cited by the Examiner UNITED STATES PATENTS 2,460,355 2/ 1949Kornernann. 2,475,109 7/ 1949 Pendleton 2201 X 2,563,118 8/1951 Jackson220-15 2,954,003 9/1960 Farrell et al 22014 X 2,993,460 7/1961 Dreyer220l5 X 3,007,598 11/1961 Beam 220l5 3,064,612 11/1962 Gardner et al220l5 3,071,094 1/1963 Leroux 220-l5 3,072,282 1/1963 Henry 220l5FOREIGN PATENTS 667,215 2/ 1952 Great Britain.

THERON E. CONDON, Primary Examiner.

JAMES R. GARRETT, Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,280,778 October 25, 1966 John Frederick Leathard It is herebycertified that error appears in the above numbered patent requiringcorrection and that the said Letters Patent should read as correctedbelow.

In the heading to the printed specification, lines 5 and 6, for"assignor to Wmn Cory G Son, Limited, London, England" read assignor, bymesne assignments, to Conch International Methane Limited, Nassau TheBahamas a company of The Bahamas Signed and sealed this 5th day ofSeptember 1967.

( AL) Attest:

ERNEST W. SWIDER Attesting Officer EDWARD J. BRENNER Commissioner ofPatents

1. THE COMBINATION IN A SHIP OF A CARGO TANK TO CONTAIN BULK LOWTEMPERATURE LIQUID AND A TANK MOUNTING TO CONSTRAIN SAID TANK FROMLATERAL BODILY MOVEMENT WITH RESPECT TO THE SHIP WHILE LEAVING THE TANKFREE TO EXPAND AND CONTRACT THERMALLY, COMPRISING TWO SERIES OF STOOLSANCHORED ON THE SHIP''S INNER BOTTOM IN ROWS EXTENDING IN TWO HORIZONTALDIRECTIONS AT AN ANGLE TO EACH OTHER AND DIAMETRICALLY OF THE BOTTOM OFTHE TANK THEREBY TO CONSTITUTE TWO DISCONTINUOUS KEYS, EACH STOOL HAVINGSIDE FACES THAT ARE EACH INCLINED TO THE VERTICAL AT AN ANGLE OF ABOUT35 TO 40* WHEREBY SAID DISCONTINUOUS KEYS CONSTITUTED BY SAID STOOLSEACH HAVE SIDES THAT CONVERGE UPWARDLY TOWARD A KEY APEX, TWO SERIES OFTUNNEL-FORM BRACKETS SECURED TO THE UNDERSIDE OF SAID TANK IN TWOHORIZONTAL ROWS PARALLEL TO AND IN SUBSTANTIAL ALIGNMENT VERTICALLY WITHSAID KEYS AND HAVING DOWNWARDLY-OPENING RECESSES WITH SIDES THAT DIVERGEDOWNWARDLY, SAID RECESSES BEING IN ALIGNMENT ALONG THE ROWS TO DEFINETWO KEYWAYS HAVING DOWNWARD DIVERGENCE CORRESPONDING TO THE UPWARDCONVERGENCE OF SAID KEYS, EACH ROW OF SAID TUNNEL-FORM BRACKETS BEINGDIRECTLY OVER A RESPECTIVE ONE OF SAID KEYS WITH AN UPPER PORTION OF THEKEY INCLUDING THE APEX THEREOF ENTERING THE KEYWAY DEFINED GY SAID ROW,ANTIFRICTION BALL MEANS MOUNTED ON SAID INCLINED SIDE FACES OF SAIDSTOOLS JUST BELOW THE APICES THEREOF, AND HARD PLATES SECURED TO SAIDDIVERGING SIDES OF THE RECESSES OF SAID TUNNEL-FORM BRACKETS WHICHPLATES BEAR ON SAID ANTIFRICTION BALL MEANS AND TRANSMIT LATERAL ANDVERTICAL FORCES BETWEEN THE TANK AND SAID STOOLS.